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Rain Management with Hugelkultur

Hugelkultur trench

Learning how to harvest rain and manage water use is an urgent topic in California where I have been visiting, but it is a big topic for all of us. It is important for us all to manage our use of that precious resource – water. My husband Henry and I have been visiting friends. We have also been visiting wonderful gardens like the Los Angeles County Arboretum and Botanical Garden, and the Huntington Library, Art Collections, and Botanical Gardens with garden writers from all over the country. It was at the Arboretum that I saw the ongoing installation of the Crescent Farm project and saw examples of hugelkultur, a technique that helps to harvest and manage rainfall. It also builds good soil and sequesters carbon.

The first thing I noticed was a deep and wide trench that had been filled up with sections of large logs with smaller spaces filled with smaller branches. The idea was to make this log filled trench stable so that if you walked on it the logs would not shift and cause a fall. The trench was strategically sited to capture the most rainfall and run-off. In California where rains are infrequent (even when there is not a serious drought) run-off and flooding are the problems that come with the heavy rains. The trench will capture the water, but it is the wood logs and branches that will absorb the water. It then takes a long time for the logs to dry out, enough time for the useful bacteria and fungi to grow and benefit the soil.

Hugelkultur example

I also saw large log sections circling a tree. Inside the circle cardboard sheets had been laid down, watered, and then covered with strips of bark to provide a mulch. I am familiar with this technique and have been using it in my new garden. I was not as familiar with the idea of providing ‘nurse’ logs to help my garden grow. The purpose of the encircling log lengths was twofold. First, to keep people from walking near the tree and causing compaction of the soil, and second, providing a medium for the growth of more helpful bacteria and fungi. The soil is a living thing; the nurse logs, and the logs in the hugelkulture trench are ways of increasing the beneficial forms of life in the soil.

I interviewed the learned horticulturist John Latsko about the making of the hugelkulture. “The whole idea is to keep the water on site in the soil, and even in the aquifer. In a really heavy rain the water may fill the trench and make the wood float, but it will not overflow,” he said. “What we want to do is slow the movement of water, spread the water, and save the water. Slow, spread and save.”

John Latsko and Yara Herrarte

He also pointed out that what looked like a berm at the edge of one of the large planting beds was a different form of hugelkulture. In this instance they had piled up logs and then covered them with soil to make a type of raised bed. “The covered bed absorbs moisture in the air and wicks it into the wood. We planted pumpkins on this bed and without any irrigation or fertilization at all we harvested a lot of pumpkins.”

I also noticed a few small trenches cut into the planting beds at a slight angle. They were going to be filled with logs, again the purpose was to capture runoff. I was told that the logs and branches used in hugelkulture can be from any kind of tree. Trees like cedar and black walnut have a reputation for being harmful in the soil and that they will kill crops planted in that soil. While it is true that some woods have volatile oils that could be harmful, they dissipate within a year and are no long a threat. All logs, hardwoods and softwoods, will breakdown and provide a source of nutrients for the plants over a long period of time. The raised beds will slowly lower themselves as the logs decompose, but they can always be added to.

The point was made that by burying these logs the gardener is also sequestering carbon Latsko told me that the soil in this garden had been heavy clay, but over the two years that the garden had been in process the soil had improved considerably.” He was aided by Yara Herrarte, a young college student who was also working in the garden as an interpretive horticulturist. That day she was getting ready to teach a workshop on lasagna gardening, which I have often mentioned here. She is preparing for her teacher certification. Her goal is to teach younger children, and to show them “that you can discover so much in the garden.”

I can tell you that I was learning a lot on this 2.2 acre garden. While the goal of the hugelkultur beds and trenches at Crescent Farm is to slow, spread and save water on site, I have a different problem. My garden site is very wet, at least seasonally. My neighbors’ garden are also wet, so I think this is an ongoing situation. I have already built some slightly raised planting beds with cardboard, compost and loam, but hugelkulture can ameliorate my problems with water too. I can dig a huglekultur trench to capture water so that I do not have standing water for as long a time, and I can build raised hugelkultur beds that will not need irrigation. Whether a trench or a raised bed the hugelkultur technique will be improving my soil. And my soil definitely needs improvement!